Friction costs a significant amount of undesirable energy and fuel consumption, decreases component lifetime, and contributes to environmentally harmful emissions. In 2009, passenger cars worldwide consumed ˜56 billion gallons of fuel (diesel and gasoline) to overcome friction in their engines, transmissions, tires, and brakes. Friction in the boundary lubrication (BL) regime is generally the most severe, and thus critically impacts fuel efficiency and lifetime of the powertrain components in motor vehicles.
Both organic and inorganic friction modifiers (FMs) have been widely used in engine oils to reduce BL regime friction. Organic FMs are generally long, slim molecules with a straight hydrocarbon chain and a polar group at one end. The effectiveness of these additives is, in a large part, determined by the ability to form an adsorbed molecular layer on a surface. This functionality can be achieved through a polar head which can undergo chemical interactions with the metal surface via physisorption or chemisorption. Enhancing the polarity of such an end group could strengthen surface adsorption of FM molecules and improve anti-friction functionality in the BL regime.